Genetic differentiation and adaptive evolution of buff-tailed bumblebees in Asia

Abstract

Bumblebees are important pollinating insects, so their declines resulting from environmental change have received intensive attention. Understanding how environmental factors shape the genetic structure of natural populations and identifying the genetic basis of local adaptation will provide insights into how bumblebees cope with environmental change. The buff-tailed bumblebee (Bombus terrestris) has a wide natural distribution range and has been domesticated to produce commercial colonies for greenhouse pollination. Previous population genetics studies on B. terrestris have mainly focused on its European populations; however, its Asian populations, representing the eastern side of its natural distribution, remain largely unsampled. To fill this gap, we collected wild B. terrestris samples from Asia, as well as wild B. terrestris samples from Europe and samples from domesticated colonies. We conducted whole-genome resequencing for 77 collected B. terrestris and performed population genomics analysis. Our results indicate that distinct genetic differentiation (FST = 0.076) exists between B. terrestris in Europe and Asia, with substantial morphological and physiological differences detected between them; B. terrestris in Asia should represent a distinct genetic resource. Demographic analysis suggests that the effective population size of B. terrestris has increased during historic cold periods, indicating their cold-adapted characteristics. Selective sweep analysis identified 331 genes under selection in the genomes of Asian B. terrestris, likely involved in their adaptation to the high ultraviolet radiation, low temperature and low precipitation of their habitats. Our research provides insights into the population genetic structure and genetic basis of local adaptation in the buff-tailed bumblebee, which will be useful for its conservation and management.